[SADXA] FW: 40m F layer Propagation DX Corridor Graphic for Phoenix - From W7EXG

[Larry Brown]

From: Bill Davis [mailto:billdav8 at q.com] 
Sent: Tuesday, December 06, 2016 7:14 PM
To: W7LB
Subject: 40m F layer Propagation DX Corridor Graphic for Phoenix -
>From W7EXG

 

Hi Larry, 

 

Attached is a graphic I presented to the SADXA Group, on the 40m F
layer Propagation Corridor. Can you please distribute this email
and attachment to the SADXA Group, as they may find value,
especially in the next 4 to 6 weeks. I think you have the
distribution list.   

 

Thanks!! Bill 

 

TO: SADXA Group

FROM: Bill Davis W7EXG

 

Although the attached graphic was developed in My Oct. 20th
presentation, I will quickly summarize for those who may not have
attended. 

 

Here are the Key Points:

 

A.  40M DAY DX can Occur in the F layer when EMUF < 7.0 MHz < MUF.

B.  After Sunrise, the EMUF builds slowly, allowing 40m F layer
DAYTIME DX along the Terminator, until EMUF exceeds 7.0 MHz. 

C.  Prior to Sunset, the EMUF decays slowly, allowing 40m F layer
DAYTIME DX along the Terminator, after EMUF decreases below 7.0
MHz. 

D.  Although the TIME and DISTANCE for 40m F-Layer Propagation is
Latitude dependent, trans-equatorial propagation is limited at the
Equator to about 2.6 Hrs, or a 40m F-Layer DX DAY Corridor
distance of about 2600 mi. 

E.  Although this propagation would appear to be a 40m Day-Time DX
Corridor, a 40m Long Path into the DARK side of the Terminator
will also emerge from the Antipode into the Long Path 40m DAY
region, taking advantage of the 40m Day Corridor. 

F.   In order to keep the 40m DX signals within the +/- 2600 mi
Propagation Corridor (and low EMUF DAY region), the Great Circle
Bearing should be within +/- 38 Degrees of the Sunrise and Sunset
Terminator. 

G.  Since the Terminator varies every day, [annually changes +/-
23.45 degrees], and the 40m Propagation Corridor changes +/- 38
degrees about the Terminator, then the angular region of the +/-
40m Propagation DX Corridor is changing every day. 

H.  The Bearing Map shows two Terminators.

a.   One Terminator at +23 degrees occurs at SR for Dec. 21st, or
SS for June 21st. 

b.   The Second Terminator is at -23 degrees (337 deg) for SS for
Dec 21st, and SR for June 21st. 

c.   The Equinox terminators on 3/21 and 9/21 are not shown, but
both SR and SS Terminators would be shown as a 0 deg to 180 deg
line. 

 

HOW TO READ THIS MAP.

 

Note on Dec. 21st, the SR terminator is +23 deg.  Thus, the 40m
F-layer DX propagation angular range  is from  345 deg to 61 deg.
(or 241 deg to 165 deg) 

(Note this covers N/E Africa, EU, and Asia and ZL land)

 

Note on Dec. 21st, the SS terminator is -23 deg (or 337 deg).
Thus, the 40m F-layer DX propagation angular range is from 299 deg
to 15 deg. (or 195 deg to 119 deg) 

(Note this covers the Far East, Asia, and South America)

 

Note the Angular Range for Dec. 21st, covers 68% of the World, and
represents the 40m F-Layer DX Opportunity for ONE DAY.. Dec. 21st.


 

The Same 40m opportunity occurs on June 21st. 

 

Thus, in the Next 4 week time period, there will be an excellent
opportunity for 40m DX 2.6 Hours before and after the Terminator,
at SUNRISE and SUNSET.

 

I KNOW I DID NOT SAY THERE WOULD BE A QUIZ, BUT THERE IS!!  

 

QUESTION: WHAT DOES THE CIRCULAR CIRCUMFERENCE OF THIS BEARING MAP
REPRESENT?  

 

Good Luck with the MUF (> 7.0 MHz) for whatever bearing you chose.
Path MUF is not always co-operative. 

 

Hopefully, someone will get their 40m DX awards in the next 4
weeks, by hanging out at the Terminators. There will be much to
hear during this time frame, and perhaps not just on 40m. 

 

You may recall, we worked HEARD on 4/2 after Tucson SS to 4:30Z.
Bands worked were 40mLP, 30m, 20m, and 17m SP. 

 

Best 73s, 

 

Bill W7EXG

W7EXG at Q.COM

 



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